1. Field of the Invention
The invention relates to a method for determining the illumination beam dose in surgical field illumination, comprising the steps of registering at least one illumination-relevant state value and calculating an illumination beam dose on the basis of the registered state value, and the invention also relates to an apparatus, an operating microscope and a computer program product therefor.
2. Description of the Related Art
In the case of surgery in which radiation-sensitive tissue has to be subjected to a certain illumination beam dose in order to be able to carry out the surgery, for example in the case of opthalmosurgical operations (eye operations), the prior art has disclosed the use of dosimeters. Such dosimeters measure the dose from an electromagnetic or particle radiation, for example the light used to illuminate the surgical region, and can be integrated into the surgical field illumination of an operating microscope.
The German laid-open specification DE 36 10 024 A1 discloses an illumination strength dose device for operating microscopes. In this, the radiation or light dose is measured by first of all sampling a small fraction of the field illumination flux generated by the microscope-internal illumination apparatus. Sampling is undertaken by arranging a transparent plane plate with sufficient scattering in the illumination beam path, with a photodetector being arranged on the edge of said plate. The electrical signal from the photodetector in respect of the radiation measured thus is then registered in a microprocessor and integrated over time.
However, this procedure does not take into account the fact that light of different wavelengths has a different effect on the radiation-sensitive tissue. It is therefore disadvantageous in that, for example, radiation of less damaging light wavelengths is evaluated the same as radiation of more damaging light wavelengths and therefore a maximum remaining surgery time estimated on the basis of the dose result is lower than what is actually possible.
This is particularly problematic if the spectral components of the light generated by the light sources vary according to desired brightness, or if the light source is interchanged during surgery or if spectral filters are used.
In order to solve these problems, the German laid-open specification DE 10 2005 055 058 A1 discloses a system that carries out a spectrally-weighted measurement of the generated light. For this, the light is measured by a plurality of sensors, for example one sensor for each of infrared, visible and ultraviolet light, and said light is registered by a microprocessor. Herein, the spectral weighting overall is attained by the respective spectral sensitivity of the sensors. The microprocessor registers the measured values weighted spectrally in this fashion, compares these to the corresponding biological radiation hazard limits and calculates the resulting remaining surgery duration therefrom.
However, the measurement elements required for this are relatively complex and expensive, and supply only limited or practically no usable results if external additional or special light sources are utilized.
Hence, it is an object of the present invention to specify a method for determining the illumination beam dose in surgical field illumination, which operates reliably, reduces the required technical complexity but nevertheless allows the effects of different light spectra and illumination situations to be taken into account.